Photocurable resin compositions, such as ultraviolet light curable resin compositions or visible light curable resin compositions, have heretofore been used often in the production of various electronic components, optical components and optical devices. Patterns of their usage include various patterns such as adhering, potting, coating, sealing, and molding. Known compositions to be used include (meth)acryl-based compositions, epoxy-based compositions, oxetane-based compositions, polyvinyl-based compositions, polyene/polythiol-based compositions, and so on. In particular, (meth)acryl-based compositions are used most frequently; urethane acrylate-based compositions, epoxy acrylate-based compositions, polyester acrylate-based compositions, and so on are used according to application. As far as junction of optical components or optical devices, polyene/polythiol-based compositions are used frequently as well as (meth)acryl-based compositions, such as urethane acrylate-based compositions.
However, with recent improvement in function of optical components and optical devices, the performance and quality which photocurable resin compositions are required to have varied and have reached high level, so that conventional photocurable resin compositions are becoming insufficient. Therefore, various studies are being carried out. Specific examples of performance and quality which photocurable resin compositions are required to have include viscosity suitable for the intended application, low odor, low outgassing, high transparency, high adhesive force, and high heat resistance.
What has recently been needed particularly is heat resistance in production. For example, in surface treatment, partial coating and the like to optical components and optical devices, deposition treatment at high temperatures over 200° C. or baking finish at high temperatures may be performed. Besides electronic components, such as IC, resistors, and inductors, optical components, such as image sensors, have come to be provided with surface mounting to their circuit boards and in such events components are made to pass through solder reflow of high temperature. In recent years, the temperature condition of solder reflow has been becoming stricter particularly with shift to lead-free solders. In such a production process, in order to improve the quality of optical components or optical devices or in order to increase productivity and production yield, parts with use of a photocurable resin composition are required to sufficiently withstand high temperature heating treatment. That is, it is necessary that none of delamination, foaming, cracks, discoloration, etc be caused by high temperature heating treatment.
Moreover, local pollution of components or devices may be caused by outgas formed in the high temperature heating treatment or the characteristics of components and devices may be lowered by outgas formed during steps or use after the components or devices are produced. In particular, with recent reduction in size and increase in precision of optical components and optical devices, the problem of lowering of characteristics caused by outgas have been becoming remarkable.
In view of such current situations, there has been disclosed a photocurable type acrylic adhesive with heat resistance and low outgassing property composed of a polybutadiene compound, a monofunctional (meth)acrylate having an alicyclic group or a linear aliphatic group, a monofunctional (meth)acrylate having a hydroxy group and/or a cyclic ether bond, a monofunctional acrylamide compound, and so on. However, both its heat resistance and low outgassing property are not high enough (see Patent Literature 1).
Moreover, a polyimide-based adhesive superior in delamination adhesion strength has been disclosed as a heat resistant adhesive, but since it will be cured by heating, it takes a long time to cure it, resulting in low productivity (see Patent Literature 2).
Furthermore, there has been disclosed a heat resistant two-main liquid component acrylic adhesive including methacrylic acid, isobornyl (meth)acrylate, and liquid rubber having a polymerizable unsaturated double bond at a terminal thereof. However, both its heat resistance and low outgassing property are not high enough (see Patent Literature 3).
Moreover, as an energy ray-curable resin composition which has high adhesion strength uniformly to various objects to be adhered, which is good in heat resistance and moisture resistance and also is superior in rigidity, and which is low in property to shrink on curing and exhibits less adhesion distortion, there has been disclosed an acryl-based adhesive including a (meth)acrylate having a main chain skeleton that is at least one member selected from the group consisting of polybutadiene, polyisoprene, and hydrogenated products thereof, having at least one (meth)acryloyl group at a terminal or on a side chain of the main chain skeleton, and having a molecular weight of from 500 to 5000, a monofunctional (meth)acrylate having an unsaturated hydrocarbon group of from 2 to 8 carbon atoms, a hydroxy group-containing (meth)acrylate, a polyfunctional (meth)acrylate, a photopolymerization initiator, and an antioxidant, but no description about heat resistance has been made (see Patent Literature 4).
Moreover, an adhesive composition including a polyfunctional (meth)acrylate, a monofunctional (meth)acrylate and a photopolymerization initiator and from which a cured body having a glass transition temperature of from −50° C. to 40° C. can be obtained has been disclosed, but there is no description about an attempt to increase the glass transition temperature of a cured body, thereby attaining sufficient heat resistance (see patent literature 5).